Solar energy is the premier green energy. The energy of solar energy reaching the ground per second is as high as 8X105kW. If 0.1% of the solar energy reaching the surface of the earth is converted into electricity, the conversion rate is 5%, and the annual power generation can reach 5.6X1012kW·h, which is equivalent to the world 40 times the energy consumption.
Solar photovoltaic power generation (PV) refers to the use of solar cell components to directly convert sunlight energy into electrical energy. Photovoltaic power generation has the advantages of few conversion links, inexhaustible resource content, high energy quality, short construction period, and close to zero emission of power generation methods.
The solar photovoltaic power generation system is composed of solar battery packs, solar controllers, and storage batteries (groups). If the output power is AC 220V or 110V, an inverter is also required. The role of each part is:
(1) Solar panels: Solar panels are the core part of the solar power system and the most valuable part of the solar power system. Its function is to convert the sun’s radiant power into electric energy, or send it to the storage battery for storage, or drive the load to work.
(2) Solar controller: The function of the solar controller is to control the working state of the entire system, and to protect the battery from overcharging and over-discharging. In places with large temperature differences, a qualified controller should also have the function of temperature compensation. Other additional functions such as light control switch and time control switch should be optional options of the controller;
(3) Batteries: generally lead-acid batteries, nickel-hydrogen batteries, nickel-cadmium batteries or lithium batteries can also be used in small and micro systems. Its function is to store the electrical energy generated by the solar panel when there is light, and then release it when needed.
(4) Inverter: The direct output of solar energy is generally 12VDC, 24VDC, 48VDC. In order to provide electrical energy to 220VAC electrical appliances, the DC power generated by the solar power generation system needs to be converted into AC power, so a DC-AC inverter is required.
Solar photovoltaic power generation products are mainly used in three aspects: one is to provide power for non-electricity occasions; the other is solar daily electronic products, such as various solar chargers, solar street lights and solar lawn lamps, etc.; the third is grid-connected power generation. It has been widely implemented in developed countries.
Since the birth of the solar photovoltaic (PV) power generation industry in the 1960s, a profound change has taken place. At first, solar photovoltaic power generation was expensive, more than US$100/(kW·h), and was only used in some ultra-high-value or remote areas, such as satellites and spacecraft.
The application potential of solar photovoltaic is that it is favored by people as a clean, carbon-free (use stage) and very low-carbon (including manufacturing) technology. Initial technological breakthroughs and advances in manufacturing technology have led energy analysts to predict that large-scale solar energy utilization is expected to replace fossil fuel power plants to a certain extent.
In the 1980s, the so-called “Public Facilities Large-scale Application Photovoltaic” system was built in South Davis, California, USA, and 1MW photovoltaic panels were installed. This large-scale photovoltaic system in a slightly remote area was put into use in the late 1990s. In 2006, the total production volume exceeded 2000MW. For the best application, the cost of installed photovoltaic facilities without subsidies is now close to 20 cents/(kW·h). This is a great progress. It is estimated that within 10 years, solar photovoltaic will become an important contributor to change global warming. Solar photovoltaics can also reduce the demand for transmission and distribution systems and provide humans with emission-free electricity, so it can directly bring benefits to urban air quality and human health.
Since the 21st century, some developed countries have formulated plans to develop renewable energy including solar cells. The research and production of solar cells have spread on a large scale in Europe, America, and Asia. In order to compete for the dominance of the global photovoltaic market, the United States and Japan are competing to introduce solar energy technology research and development plans. For example, by 2010, the United States plans to install 4600MW (including the “Million Roof Solar Project”), and Japan plans to install 5000MW (Japan “New Sunshine Project”).
According to forecasts by European, Japanese and other energy institutions, solar photovoltaic power generation will account for 1% of global power generation in 2020; 21% of global power generation in 2040; and around 2050, solar energy will become the world’s main alternative energy source.